1. Field of Invention
The invention relates to wireless communications, and more specifically to a variable duty cycle mixer module that is configured to select one of multiple duty cycles for the local oscillator depending on the performance of the mixer with respect to one or more radio access technologies.
2. Related Art
Wireless communication devices, such as cellular telephones to provide an example, are becoming commonplace in both personal and commercial settings. The wireless communication devices provide users with access to all kinds of information, as well as the ability to communicate with other such devices across large distances. For example, a user can access the internet through an interne browser on the device, download miniature applications (e.g., “apps”) from a digital marketplace, send and receive emails, or make telephone calls using a voice over internet protocol (VoIP). Consequently, wireless communication devices provide users with significant mobility, while allowing them to remain “connected” to communication channels and information.
Wireless communication devices communicate with one or more other wireless communication devices or wireless access points to send and receive data. Typically, a first wireless communication device generates and transmits a radio frequency signal modulated with encoded information. This radio frequency signal is transmitted into a wireless environment and is received by a second wireless communication device. The second wireless communication device demodulates and decodes the received signal to obtain the information. The second wireless communication device may then respond in a similar manner. The wireless communication devices can communicate with each other or with access points using any well-known modulation scheme, including simple amplitude modulation (AM), simple frequency modulation (FM), quadrature amplitude modulation (QAM), phase shift keying (PSK), quadrature phase shift keying (QPSK), and/or orthogonal frequency-division multiplexing (OFDM), as well as any other communication scheme that is now, or will be, known.
During communication, signals received by the wireless communication device are provided to a mixer, which is generally employed to shift the frequency of the received signals. This can be used, for example, to shift a modulated signal to a baseband frequency.
In non-linear systems, including mixers, the second order intercept point (IP2) is a measure of linearity that quantifies the second-order distortion generated by nonlinear systems and devices. In a wireless transceiver, any leakage from the transmitter into the receiver chain, can exacerbate second order distortion because of the relatively high amplitude level of the transmit signal. As such, improving IP2 of the receiver chain has become imperative in modern communication standards.
Therefore, the standards of most modern RATs (radio access technologies) define strict IP2 levels that must be achieved by mixers that are used with those RATs. For example, the 2G wireless standard (incorporated herein by reference in its entirety) requires approximately 40 dB of IP2 level, the 3G specification (incorporated herein by reference in its entirety) requires approximately 45 dB of IP2 level, and the 4G specification (incorporated herein by reference in its entirety) requires approximately 52 dB of IP2 level.
Because of manufacturing variables, different mixers produce different IP2 performance. However, because any of 2G, 3G and 4G modes share the same RF frequency range, it would be beneficial to employ only a single mixer for receiving signals within each such RAT.
The disclosure will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.